title: Squeezing and expanding light without reflections via transformation optics.
abstract: We study the reflection properties of squeezing devices based on transformation optics. An analytical expression for the angle-dependent reflection coefficient of a generic three-dimensional squeezer is derived. In contrast with previous studies, we find that there exist several conditions that guarantee no reflections so it is possible to build transformation-optics-based reflectionless squeezers. Moreover, it is shown that the design of antireflective coatings for the non-reflectionless case can be reduced to matching the impedance between two dielectrics. We illustrate the potential of these devices by proposing two applications in which a reflectionless squeezer is the key element: an ultra-short perfect coupler for high-index nanophotonic waveguides and a completely flat reflectionless hyperlens. We also apply our theory to the coupling of two metallic waveguides with different cross-section. Finally, we show how the studied devices can be implemented with non-magnetic isotropic materials by using a quasi-conformal mapping technique.
authors.affiliation: Valencia Nanophotonics Technology Center, Universidad Politécnica de Valencia, 46022 Valencia, Spain. cargarm2@ntc.upv.es
authors.forename: C
authors.initials: C
authors.lastname: García-Meca
authors.forename: M M
authors.initials: MM
authors.lastname: Tung
authors.forename: J V
authors.initials: JV
authors.lastname: Galán
authors.forename: R
authors.initials: R
authors.lastname: Ortuño
authors.forename: F J
authors.initials: FJ
authors.lastname: Rodríguez-Fortuño
authors.forename: J
authors.initials: J
authors.lastname: Martí
authors.forename: A
authors.initials: A
authors.lastname: Martínez